Carrera Mike

CDODKIN,

Sorry, I was out of town. Just logged in today since I left. I have read in a couple of german auto magazines, and one of them is Excellence, and also from a PCA Tech Rep that the 996 suspension was not engineered to have 19 rims. The geometry of the linkages are maxed out to use 18 rims. The car feels ok in normal driving, until you hit those bumps where the feedback to the steering wheel is really pronounced and you could feel a slight pull to one side. Now Porsche motorsports in CA has racing linkages/arms to configure/modified to take the 19s. As you lower the 996, just with the 18 alone, the rear are already almost out of limits for the factory street spec allignment on the camber/toe in. /Of course I'm not a pro.. I'm just basing this from what I read and talking to master mech at Porsche of Midlothian, VA.

cdodkin

I don't get it - rolling radius is exactly the same, so how does changing up to 19" effect the geometry?

Anyone?

wross996tt

Agreed, the ride is certainly rougher (with less rubber between rim and road) however geometry is geometry. But I'm willing to learn.

996superfly

Yes, I do have 19" with Toyo's. Ride is a little harsh due to lower profile. No problem with bigger wheels. I did have Hergesheimer MotorSports aligned my car. Mark (owner) told me that he did some tweaks to it, but 996 with 19" is OK. Now the ride is so much better than before when I had 18" OEM Carrera 5 spoke.

carpundit

This is a helpful discussion. I recall reading that 18" is as far as you want to go on the 996, but I don't recall why. Could it have been something to do with an affect on vibration?

Anyone have any comment on whether it's hard to clean wheels that have those boltheads on the inner circumference?

Steven C.

Typically wheel size limitations are based on the strength of the suspension components to handle the increased strees put on them from less rubber and air between them and the pavement. And clearance.

JimB

Here's the issue with 19s on a 996 as I see it. If you mount 19s with 997 size tires the taller diameter will effectively increase your R&P ratio making your car slower. If you use the very low profile xxx/25/19 tires you have almost no sidewall and almost no sidewall flex. This might sound good for handling but it isn't. I learned about this when a Hoosier engineer explained why I shouldn't run 285/30/18s on the back of my racecar. Without getting too deep into something that I really don't understand very well, the tire sidewall is designed to mange both acceleration torque and turning torque. (I'm kind of making this terminology up but the basic idea is there.) Think of your car accelerating out of a corner. The tire engineers want the tire to be flexing just enough both sideways and backwards to maximize the tire adhesion. If it's too small you'll reduce the effectiveness of the tire when under stress. So, in all likelihood, you'll get poorer performance from 19s.

Having said that, I'm on the waiting list for a set of 19s for my street car. Go figure.
Jim

cdodkin

As you say Jim, I don't think the lower profile tires present any issues for street use.

I went with 235/35/19 and 315/25/19 (Front/Rear) with my 19"s, and I'm happy with the way the car handles.

I don't see people with 19" rims on the track, so you're tire man probably has a good point.

For me, 19" is all about the look of the car - without compromising my day to day driving

996superfly

Tito cdodkin! Mine is for street use only. I don't go 60 mph around turn. Just for the good look. Sidewall or no sidewall, it doesn't effect my ride much.

Cool996

HRE 841 on PS2's 19x8 and 19x11

Red141

Jim, what size tires front & rear did he recommend for the track?

MasterMason11

Here's mine... HRE 545R Black Anodized...

JimB

They recommend either 295 or 315/30/18 in back and 245/35 or 40/18 in back. I use 315/30/18 and 245/35/18.

BTW, here are my favorite wheels.

Merry Christmas.
Jim

Dale Tillman

Great posts! The PO put some rash on the wheels and I had a missap with a curb (duh!) so I need to either get these replaced with the same or move on to different wheels...I really like these wheels...anyway, does anybody know exactly what wheels I have? They are 18's and I think they came with the car but can't confirm.

Dale Tillman

here are the wheels...